Roughly 69,000 people have evacuated the Kumamoto Prefecture where at least 100,000 homes lost electricity and 385,000 are without running water, Suga said.

On Saturday afternoon, 2,000 soldiers were active in the rescue and relief efforts following the two quakes, but Suga said that number will increase to 15,000.

There have been no irregularities reported at any of the nuclear power plants in the region, according to Suga.

College students carry blankets and food toward a gym-turned shelter as a damaged apartment building is seen in the background after an earthquake in Minamiaso village, Kumamoto prefecture, Japan, April 16.Yuki Sato / Kyodo News via AP

Saturday's earthquake briefly triggered a tsunami advisory that the Japan Meteorological Agency later lifted. At least five aftershocks rattled the region, the strongest of which was a magnitude-5.8, the USGS said.

Since Saturday's quake was bigger, Thursday's was technically a foreshock, a Meteorological Agency official, Gen Aoki, told a news conference.

"In those areas where the tremors were strong, there is a higher risk of homes collapsing and landslides so we urge everyone to pay particular attention to tremors and rain," Aoki said.

The Fire and Disaster Management Agency said 66 people were trapped inside a nursing home in Mashiki, the hardest-hit town, and rescue efforts were underway, the AP reported. No other details were immediately available.

"The shaking was so violent I couldn't stand still," said Hironobu Kosaki, a Kumamoto police official, after Thursday night's quake.

Police officers check a collapsed house after an earthquake in Mashiki town, Kumamoto prefecture, Japan, on April 16, 2016.Kyodo News via Reuters

There was a glimmer of good news after Friday's devastation: A baby who was buried under rubble for hours was rescued unscathed.

U.S. State Department spokesman John Kirby said the U.S. has been in touch with authorities in Japan and isn't aware of any Americans who have been affected by the quakes.

"Our thoughts and prayers go out to everyone affected by the earthquake, this second one as well, and we are monitoring it as best we can," he said at the State Department briefing Friday.

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